<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <!-- 编写函数，判断一个字符串的内容是不是纯数字 -->
    <script>
        var inptNum=prompt("请输入一段字符");
        function num(a){
            if(Number(a)){
                alert("该字符串内容是纯数字");
            }else{
                alert("该字符串内容不是纯数字");
            }
        }
        num(inptNum);
    </script>
</body>
</html>